1. Field of Invention
The present invention relates to an optoelectronic semiconductor device, and more particularly to a method and product for dicing an optoelectronic semiconductor wafer that combines a laser scribing and a diamond saw dicing and reduces wear of diamond saws.
2. Description of the Related Art
Optoelectronic semiconductor devices such as blue LEDs are used widely in display, illumination and data storage technologies. Because red, green, and blue are the primary colors that are mixed to display the color of pixels on a computer monitor, high-brightness blue-light LEDs are more and more important in the application of color monitors. Because of short wavelength of blue light, blue LEDs are also used as light sources in data storage and access technology. In addition, white LEDs improved from blue LEDs are considered important in next generation illumination technology.
Wafers of blue and white LEDs generally comprise a sapphire substrate and an epitaxial layer formed epitaxially on the sapphire substrate. Wafers of blue and whites LEDs are separated typically into multiple dies by diamond saw dicing process or laser dicing process. With reference to FIG. 6, when a wafer is separated by diamond saw dicing process, the sapphire substrate of the wafer is mechanically scribed with a diamond saw to define multiple guide grooves (80) with a depth in several um on the sapphire substrate. Finally, the wafer is broken into multiple dies along the guide grooves (80) by means of a breaking machine. Because of the extreme hardness of the sapphire substrate, the diamond saw is usually worn off seriously after the diamond saw dicing process and this causes high operating and manufacturing costs. Additionally, because the conventional diamond saw dicing process is sharp pointed scribing and usually causes lateral and radial cracks at two sides of the guide grooves (80), the wafer often does not break completely along the guide grooves (80) and this causes chipping and cracking of the dies. So appearances of the dies may be bad and die yield is reduced.
With reference to FIG. 7, the conventional laser dicing process uses lasers to substitute for diamond saws to perform scribing. Because guide grooves (90) formed by the laser dicing process have a high aspect ratio, dies after breaking have better appearances. Manufacturing costs of the dies are also reduced because of no wear of diamond saw. However, the conventional laser dicing process usually causes black layers formed in the guide grooves (90). So the dies have black areas on the surfaces of the dies and this affects the light extraction efficiency of the dies.
Because the dicing process is a back-end manufacturing process of semiconductor devices, expensive costs of the front-end manufacturing processes are wasted if dicing process is not performed well and causes discarding of the dies. Consequently, dicing process is very important for manufacturing optoelectronic semiconductor devices such as blue LEDs.
To overcome the shortcomings, the present invention provides a method and product for dicing an optoelectronic semiconductor wafer to mitigate or obviate the aforementioned problems.